chapter 2 computer network technology network management principles and practice 1vikas singh, csis...
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Chapter 2
Computer Network Technology
Network Management Principles and Practice
1Vikas Singh, CSIS Dept., BITS Pilani
Technology and Management
• What are the technologies that need to managed?
• Challenges of technological progress on
network management
2Vikas Singh, CSIS Dept., BITS Pilani
Computer Network Technology• Network comprises
• Nodes• Links
• Topology: How they’re configured• LAN• WAN
• Question: Distinction between LAN and WAN?
3Vikas Singh, CSIS Dept., BITS Pilani
LANs• Type of LANs
• Ethernet• Fast Ethernet• Gigabit Ethernet• Half-duplex vs Full-duplex• Switched Ethernet• VLAN• Token ring• FDDI• ATM / LANE
• Token ring, FDDI and ATM/LANE not used in newer implementation!
4Vikas Singh, CSIS Dept., BITS Pilani
Nodes• Hubs
• Bridges
• Remote bridges
• Routers
• Gateways
• Half bridge / half router
• Switches
5Vikas Singh, CSIS Dept., BITS Pilani
WANs• Facilities / Media• Wired
• Copper• Coaxial• Fiber
• Wireless• Terrestrial• Satellite
• Mode: Digital, Analog
• Services• POTS• ISDN• Broadband: Frame Relay, ATM, MPLS VPNs etc• Wireless services
6Vikas Singh, CSIS Dept., BITS Pilani
Basic LAN Topologies
Figure 2.1(b) Ring Topology
Figure 2.1(a) Bus Topology
Ethernet
DTE DTE DTE
DTE DTE
DTE
DTEDTE
DTE
• Bus topology• Used in Ethernet LAN family• Common shared medium• Randomized access (CSMA/CD)• Easy to implement• Lower utilization under heavy traffic 30%-40%• Single culprit could effect the entire LAN• A malfunctioning cable can disrupt the entire communications on
the Ethernet segment7Vikas Singh, CSIS Dept., BITS Pilani
Basic LAN Topologies
Figure 2.1(b) Ring Topology
Figure 2.1(a) Bus Topology
Ethernet
DTE DTE DTE
DTE DTE
DTE
DTEDTE
DTE
• Ring Topology• Used in token ring and FDDI• Shared medium• Deterministic access• Master DTE has control• High utilization >90%
8Vikas Singh, CSIS Dept., BITS Pilani
Star & Hybrid LAN Topologies
DTE
DTE
DTE
DTE
Figure 2.1(d) Hub Configurations
DTE
DTE
DTE
DTE
Token Ring HubEthernet Hub
• Star topology used with bus and ring topology • Hub is “LAN in a box”• What does the electronic LAN inside the box
look like?• Why has hub become so popular?
Figure 2.1(c) Star Topology
DTE
DTE
DTE
DTE
DTE DTE
9Vikas Singh, CSIS Dept., BITS Pilani
A Campus Network
Ethernet 10.1.1.0
10.1.1.2 10.1.1.3 10.1.1.4 10.1.1.5
Bridge
Ethernet 10.1.2.0
10.1.2.2 10.1.2.3 10.1.2.4 10.1.2.5
10.1.2.6
10.1.1.1
Router
10.1.2.1
FDDI Ring10.10.0.0
Token-ring10.2.1.0
Router
Half-R
outer
Hal
f-Rou
ter
Eth
erne
t 10.
3.1.
0
Figure 2.3 Campus Network of LANs
ATM ELAN 10.4.1.0
Router
Router
ExternalNetwork
• ATM VLAN an alternative to FDDI backbone• The Ethernet advances in Hub/switching technology and speed
have unified the LAN/MAN, since even in the backbone one can use Fast Ethernet or gig Ethernet.
10Vikas Singh, CSIS Dept., BITS Pilani
WAN Topologies
N3
N4
N2
N5N1
Figure 2.2(a) Mesh Topology
N6
N1
N2 N3
N6N5N4
Figure 2.2(b) Tree Topology
• Mesh topology• Implemented in network layer level• Multiple paths between nodes• Flat topology• Redundancy• Load balancing• Shortest path
• Tree topology• Used with Ethernet bridges • Hierarchical• Efficient for small networks and
special purpose networks11Vikas Singh, CSIS Dept., BITS Pilani
Notes
Ethernet
• IEEE 802.3 standard• 10 Mbps data rate• Collision - analogy of hollow pipe• Principle of operation; CSMA/CD• Segment length and drop cable length• Minimum size of packet 64 bytes• Maximum size of packet 1500 bytes• Hub configuration
Table 2.1 Ethernet LAN Topology Limits
TYPE DESCRIPTION SEGMENT LENGTH DROP CABLE
10Base2 Thin coax (0.25”) 200 meters Not allowed
10Base5 Thick Coax (0.5”) 500 meters Twisted pair: 50 meters
10Base-T Hub topology N/A Twisted pair: 100meters
10Base-F Hub topology N/A 2 km
12Vikas Singh, CSIS Dept., BITS Pilani
Ethernet Cont’d)• In Thin Ethernet the workstations etc are daisy chained. Hence a Coax cable
problem in a segment can partition the segment in 2, and disrupt the communications.
• The disdvantages of the Bus topology?
13Vikas Singh, CSIS Dept., BITS Pilani
Ethernet Cont’d)• In any new networks the 10Base2 and 10base 5 Ethernets
are not used• In practice Ethernets based on Hub technology are used• Advantages
– Star topology– Uses standard Cat 3 wiring– A break in the wiring only affects a single user– Easy to trouble shoot
14Vikas Singh, CSIS Dept., BITS Pilani
Fast Ethernet
• Rationale • Max drop length 100m => Max round-trip
time 1/10 of Ethernet; hence 10 times data rate• Standard 100Base-T4• Compatibility with 10BaseT• UTP limitation; Use 4-pair UTP @ 25 Mbps/pair• Alternatives: 2-pair 100BaseTX Cat 5(Max 100 m)
and 100Base FX optical fiber (Max 2 km)
PMD Sublayer
Convergence Layer
MAC Sublayer
LLCData Link
Physical
Network
Figure 2.4 100Base-T Fast Ethernet Protocol Architecture
LLC Logical Link controlMAC Medium Access ControlPMD Physical Medium Dependent
Hub Station4-pair UTP
15Vikas Singh, CSIS Dept., BITS Pilani
LAN Data Rate RaceE’Net
10Mbps
FDDI100 Mbps
Fast E’Net100Mbps ATM
155.52 MbpsGbit E’Net
1 Gbps
DuplexE’nets
ATMOC-n
16Vikas Singh, CSIS Dept., BITS Pilani
Gigbit EthernetTable 2.2 Gigabit Ethernet Topology Limits
9micronSingle-Mode
50micronSingleMode
50 micronMultimode
62.5micron
Multimode
BalanceShielded
Cable
UTP
1000BASE-LX 10 km 3 km 550 m 440 m - -
1000BASE-SX - 550 m 260 m - -
1000BASE-CX - - - 25 m -
1000BASE-T - - - - 100 m
• Packet size 512 bytes, slot size 4.096 microseconds• Minimum frame size 64 bytes for backward compatibility; Slot
filled with carrier extension• Packet bursts with no idle time between frames
increases efficiency
17Vikas Singh, CSIS Dept., BITS Pilani
Switched Ethernet
Switchedhub
DTE
DTE DTE
DTE
DTE DTE
DTE DTE
Figure 2.8 Switched Ethernet Hub
• Maximum throughput increased ~N/2 in N-port hub
18Vikas Singh, CSIS Dept., BITS Pilani
Client/Server Configuration usingSwitched Hub
Server
Switched hub
Workstation Workstation Workstation
10 Mbps 10 Mbps
10 Mbps
100 Mbps
Figure 2.9 Switched Hub in Client-Server Configuration
19Vikas Singh, CSIS Dept., BITS Pilani
Virtual LAN
RouterSwitched Hub
DTE 1
DTE 2
DTE 3
DTE 4
DTE 5VLAN
200.100.150.1VLAN
200.100.160.1
Port for Subnets200.100.150.1
&200.100.160.1
Figure 2.10 Virtual LANs
• Switched hub enables establishing virtual LANs • Permits switching stations between LANs without
physical moving of equipment• Walk through scenario
20Vikas Singh, CSIS Dept., BITS Pilani
Token Ring
• Adopted by IBM• IEEE 802.5 standard• Data rates of 4Mbps and 16 Mbps• Single and dual ring LANs
DTE 4
DTE 3DTE 1
DTE 2
Figure 2.11 Token Ring LAN
TokenRing
3 to 1 ACK
1 to 3 MSG
DTE 1 hastoken control
21Vikas Singh, CSIS Dept., BITS Pilani
Dual Ring TR LAN
Figure 2.12(a) Token Ring Dual Ring Management
DTE 4
DTE 3DTE 1
DTE 2
RedundantRing
PrimaryRing
22Vikas Singh, CSIS Dept., BITS Pilani
Failure Recovery in TR LAN
• Station failure recovery• Link failure recovery
DTE 4
DTE 2
DTE 3DTE 1
Figure 2.12(b) Token Ring DTE Isolation
Failed Station
Figure 2.12(c) Token Ring Segment Isolation
DTE 4
DTE 2
DTE 3DTE 1
23Vikas Singh, CSIS Dept., BITS Pilani
FDDI
Figure 2.13(a) Dual Ring FDDI Network Configuration
DAS
SASSAS
DAS
SAS Single Attached StationDAS Dual Attached Station
• Uses fiber optics medium• Modified token ring protocol• Data rate 100 Mbps• Segment length 100 km• 500 stations in the ring with max separation of 2 km• Single and dual attached stations• Dual attached stations load share the two rings
24Vikas Singh, CSIS Dept., BITS Pilani
Basic Network Nodes
Routing
ATM Switch
ATMATM
Figure 2.14(a) Switch
Bridge
Local LANEthernetPackets
Figure 2.14(b) Bridge
Filter
Router
Local NetworkIP Packets
Figure 2.14(c) Router
Filter Routing
Figure 2.14 Basic Network Node Components
Gateway
X.25NetworkPackets
IPNetworkPackets
Figure 2.14(d) Router
Formatchange
External LANEthernetPackets
External NetworkIP Packets
25Vikas Singh, CSIS Dept., BITS Pilani
Network Node Components
• Hubs• Bridges• Remote bridges• Routers• Gateways• Half bridge / half router• Switches
Router
SwitchedHub
Bridge
RemoteBridge
ATMSwitch
GatewayExternalNetwork
HalfRouter
Router HubWorkstation
Dial-upNetwork
ExternalNetwork
Figure 2.15 Networked Components
Hub
Hub
26Vikas Singh, CSIS Dept., BITS Pilani
Notes
Hubs
• Hub is a platform• Function dependent on what is housed
• LAN• Switched LAN• Bridge
Hub
Patch Panel
DTE DTE DTE DTE
Wiring Closet
Figure 2.16(a) Hub Configuration
27Vikas Singh, CSIS Dept., BITS Pilani
Notes
Stacked Hubs
Hub 2
Hub 1
BackplaneInterconnection
To D
TEs
Figure 2.16(b) Stacked Hub
• Hub ports can be scaled up using stacked hubs• Stacked hub
• extend back plane• connected as daisy chain
28Vikas Singh, CSIS Dept., BITS Pilani
BridgesBridge
Local Bridge Remote Bridge
SimpleMultiport
MultiportMulti-protocol
• Bridges two nodes at data link control layer• Ethernet: tree topology, transparent bridge• Token ring:mesh topology, source routing bridge
• Remote bridge uses WAN interface cards; same protocol used at both ends
• Ethernet bridge is a learning bridge
29Vikas Singh, CSIS Dept., BITS Pilani
Routers
Protocol interface
Physical medium A
TP
NP
DP
Phy
TP
NP
DP'
Phy'
Router
Network AProtocol P
Network BProtocol P
Router
NP
DP
Phy
NP
DP'
Phy'
Figure 2.21 Router Configuration
Physical medium B
• Routers operate at network layer• Routes packets between nodes of similar
network protocols• Routing table used to route packets• DLC and Physical layers could be different
under the same common network layer protocol
30Vikas Singh, CSIS Dept., BITS Pilani
Gateway
Protocol interface
Physical medium
TP
NP
DP
Phy
TP
NP'
DP'
Phy'
Gateway
Network AProtocol P
Network BProtocol Q
Gateway
NP
DP
Phy
NP'
DP'
Phy'
Figure 2.22 Gateway Configuration
• Gateway is router connecting two networks with dissimilar network protocols
• Gateway does the protocol conversion at the network layer• Protocol converter does the conversion at the application layer
31Vikas Singh, CSIS Dept., BITS Pilani
Tunneling
IP
MultiprotocolRouter
X.25
MultiprotocolRouter
IP
Ethe
rnet
Ethe
rnet
Tunnel
Figure 2.24 Tunneling Using Multiprotocol Routers
Joe’s MobileLoc: Seattle
SallyL.A
Home LANNYTunneling Foreign
Agent
• Tunneling is transmission of packets (via multiprotocol routers) by encapsulation
• In Figure 2.24, packets are encapsulated and transmitted through X.25 network in a serial mode
• In the mobile environment, Joe and his home agent in NY communicate Joe’s Seattle location to the foreign agent. His communication with Sally in LA is tunneled
• Other examples of tunneling are layer 2 tunneling protocol (L2TP), used for dial up services offered by ISPs 32Vikas Singh, CSIS Dept., BITS Pilani
Half-Bridge
Router Bridge Ethe
rnet
PPP/MP
SerialOutput
Figure 2.25 Half-Bridge Configuration
• Half-bridge (also referred to as half-router) is for point-to-point communication
• Uses PPP protocol• Helps low-end users to communicate with ISP on dial-up link
saving the expense of dedicated link• Router encapsulates packets in PPP frames and puts serial
outputs to the bridge, and vice-versa
33Vikas Singh, CSIS Dept., BITS Pilani
Switched Networks
• Switches are embedded in bridges and routers• Switched network used in WAN • Two types of switched networks
• Circuit-switched• Packet-switched
• Datagram service• Virtual circuit
B
A D
C
DTE A DTE Z
Pkt3 Pkt2 Pkt1Pkt2 Pkt3 Pkt1
Pkt1Pkt3
Pkt2
Pkt2Pkt2
Figure 2.26(a) Datagram Configuration
B
A D
C
DTE A DTE Z
Pkt3 Pkt2 Pkt1Pkt3 Pkt2 Pkt1
Pkt3
Pkt2
Pkt1
Figure 2.26(b) Virtual Circuit Configuration
34Vikas Singh, CSIS Dept., BITS Pilani
Transmission TechnologyTransmission Technology
Medium Mode
Wired Wireless
LAN WAN
Digital Analog
LAN Mobile Satellite
• Physical transport media• UTP• Coax• Fiber• Terrestrial wireless• Satellite transmission
35Vikas Singh, CSIS Dept., BITS Pilani
Transmission Modes
Figure 2.27(c) Cell Transmission (ATM)
Figure 2.27(b) Packet Transmission ( X.25)
User 1 User 2 User 3 User 4User 24
Time
Ch
an
ne
lB
an
dw
idth
Time
TimeDivision
Multiplexing(TDM)
User 2 User 3 User 4 User 5User 1
Time
Ba
nd
wid
th
Figure 2.27(a) T1 Time Division Multiplexing (TDM) Transmission
PacketMultiplexing
Ba
nd
wid
th
Time
CellMultiplexing
channel 2
channel 1
channel 24
36Vikas Singh, CSIS Dept., BITS Pilani
Questions
• What kind of switching is used in conjunction with TDM? With Cell transmission?
• Is there any other mode we have missed in last slide?
37Vikas Singh, CSIS Dept., BITS Pilani
Broadband Services
SDH / SONETWAN
CampusATM / LAN
Network
CampusATM / LAN
Network
ResidentialCustomerNetwork
ResidentialCustomerNetwork
OC-n /STS-n
Link
OC-n /STS-n
Link
Figure 2.28 Broadband Services Network
ServiceProviders
Gateway
BroadbandAccess
BroadbandAccess
• Integrated services: Voice, video, and data• Narrow band ISDN (Integrated Services Digital Net.)
• Basic rate:2B + D (B channel 64 kbps and D channel 16 kbps
• Primary rate: 23B + D channels • Broadband (ISDN) Services uses ATM technology
• SONET (Synchronous Optical Network) or SDH (Synchronous Digital Hierarchy)
• Data rate OC-n• OC-1 51.84 Mbps• OC-3 155.52 Mbps
• Access technologies:• HFC (Hybrid Fiber Coaxial) / Cable modem• ADSL (Asymmetric Digital Subscriber Line)
38Vikas Singh, CSIS Dept., BITS Pilani
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